This invention relates generally to the testing of circuits on a computer backplane and more particularly relates to a method and apparatus to test hot-plug circuits corresponding to each slot on an active computer backplane.
Internal computer components, such as processors, cache, memory, expansion cards and storage devices, communicate with each other over one or more busses. A bus, in computer terms, is a channel over which information flows between one or more devices. A bus normally has access points, or places into which a device interfaces in order to become part of the bus. Once a device interfaces with the bus, the device can send information to, and receive information from, other devices which are also interfaced to the bus.
Nearly all PCs made today include a local bus for data that requires especially fast transfer speeds, such as video data. The local bus is a high-speed pathway that connects peripherals (e.g., video cards, sound cards, modems, etc.) directly to the processor. Currently, the most popular local bus is the Peripheral Component Interconnect (PCI) bus, which was developed by Intel Corporation, and introduced in 1993.
One of the most important advancements in the PCI bus in recent years is the addition of hot plug technology. Hot plugging is generally defined as the ability to add and remove devices to a computer while the computer is running and where the operating system automatically recognizes the change. The PCI Special Interest Group has developed an open, industry standard that enables multiple system providers, operating system developers, and adapter suppliers to implement PCI hot-plug solutions. Unlike older bus architectures, PCI hot-plug technology allows a PCI adapter to be added, removed or replaced while the host system is running and while other adapters in the computer system provide uninterrupted service. As a result, PCI hot-plug technology significantly reduces unplanned system downtime. In the past, reliable and powerful around-the-clock performance was available only from expensive, proprietary systems.
A major challenge for manufacturers of PCI backplanes that support hot-plug circuits is the functional testing of the PCI hot-plug circuits themselves (i.e., whether the hot-plug circuits power-up/power-down the associated adapter slot properly). Hot-plug circuits are not fully testable by a standard backplane manufacturer""s in-circuit-test (ICT) because the sense resistors in the hot-plug circuit are of too low of a resistance to differentiate from a short. As a result, testing of the hot-plug circuits would have to be performed by two separate test adapter cards (i.e., an analog card for analog testing, and a digital card for digital testing) that are placed in a PCI slot corresponding to the hot-plug circuit under test. This effectively doubles the time the backplane resides at a testing station, and greatly increases the cost and complexity of the backplane testing mechanism.
Thus, there is a need for a quick, cost-effective method and apparatus for testing PCI hot-plug circuits on an active PCI backplane of a computer system after manufacture. The method and apparatus should allow an analog test to be performed by the same manufacturer""s test adapter that performs digital PCI testing of the slot, thus reducing the time the backplane resides at the test fixture. The method and apparatus should also improve development testing of PCI hot-plug circuits on a PCI backplane, enabling detailed laboratory measurements to be taken directly from the PCI backplane via an external test connector.
These and other objects, features and advantages of the present invention will be further described and more readily apparent from the summary, detailed description and preferred embodiments, the drawing and the claims which follow.
The present invention provides an apparatus and method for testing hot-plug circuits on a computer backplane. In a preferred embodiment, a test connector on each backplane routes signals to/from an external tester to the backplane, and more specifically, to the hot-plug circuits that control power supplied to each of the card slots mounted on the computer backplane.
The test connector enables an external tester to turn on each card slot present on the computer backplane. The external tester then directs a test adapter card residing in a selected card slot to apply a nominal and overcurrent load to each voltage level of the selected card slot. After each load has been applied, the corresponding voltage level is returned to the external tester. The external tester then measures the voltage level, and verifies that the voltage level falls within a predefined voltage range. The test connector uses existing unutilized bus signal lines to pass test directives and results between the card slot under test and the external tester. The same test adapter card that performs the analog test on a card slot is also used to perform digital testing on the card, thus reducing both testing time and the complexity of the testing apparatus.
The present invention offers several advantages over current methods of testing hot-plug circuits. The preferred embodiment allows analog testing of the hot-plug circuits to be performed by the same test adapter that performs digital testing, cutting potential testing time in half. Since a single test adapter card can be used for both the analog and digital tests, the complexity of the fixture required to perform the circuit testing is reduced. Finally, the preferred embodiment provides improved development testing of hot-plug circuits, since detailed laboratory measurements can be obtained quickly and easily via the test connector.